Cold spots in a heated house and a lack of airflow seem to cause mold. The temperature difference causing condensation, excess moisture with nowhere to go and then mold.

Interesting whether this would happen in an entirely unheated building.

I suppose it depends if there is some types of poorly placed barriers. In structures that can breath readily and in climates where they can dry it is less of an issue. On other hand those also need to in general be protected from water in structures.

A lot of that is due to structures not having a proper vapor barrier, therefor allowing vapor exchange from the outside world which decreases in-wall condensation.

It does if it experiences any kind of a diurnal heating cycle from the sun.

Moist air from cooking increases the humidity in the house. The walls of the house are cold, the moisture condenses on the cold walls keeping them damp for the entire winter.

If you're thinking, "but I don't cook soup that much", remember the chemical equation for burning methane with oxygen.

Or just humans breathing. And plants. Pets too.

In areas with coastal fog it can be the case that the cooler months with lower evaporation rates are more likely to allow spores a foothold. This is often seen in older spaces designed with passively vented kitchen and baths.

But good building design following current standards isn't going to be affected by this.

Life has had half a billion years to figure out that if you produce offspring at the optimal (min-maxed, really) survival time, you get more offspring.

It's not just that spores work better in certain weather conditions, it's also that there are often more spores in those conditions as well. Mushrooms coming up after a rain, gambling that there will be another one in a couple days, for instance.